The prior art includes an assembly comprising a package and at least one outlet wherein, in use, an inner space of the package is filled with fluid to be dispensed, wherein in the inner space of the package there prevails a pressure for enabling dispensing the fluid via the outlet, the assembly further comprising a pressure control device connected to the outlet adjacent the outlet, for feeding the fluid to the outlet via the pressure control device at a predetermined constant pressure which is independent of and less than the pressure prevailing in the inner space of the package, the pressure control device comprising a housing provided with an inflow opening, an outflow opening and a fluid flow path extending in the housing between the inflow opening and the outflow opening, the inflow opening being in fluid connection with the inner space of the package and the outflow opening being in fluid connection with the outlet, the pressure control device being located in the proximity of the outlet and further comprising a controllable seal for releasing and closing the fluid flow path and a pressure sensor element accommodated in the housing for movement between a first and a second position, the pressure sensor element in the first position controlling the controllable seal to release the fluid path and in the second position controlling the controllable seal to close off the fluid path, the pressure sensor element on the one hand being exposed to the pressure prevailing in the fluid path downstream of the controllable seal, and on the other being exposed to a predetermined force which, in use, determines the predetermined pressure, wherein, in use, the pressure sensor element moves in the direction of the first position when the pressure prevailing in the fluid flow path downstream of the seal drops below the predetermined pressure determined by the predetermined force and the pressure sensor element moves in the direction of the second position when the pressure prevailing in the fluid flow path downstream of the seal rises above the predetermined pressure determined by the predetermined force.
Such assembly is known per se. In this respect, one may think of an aerosol can, a vessel or a bag-in-box, filled with a fluid to be dispensed. This fluid may be a gas as well as a liquid. When a fluid is a liquid, this may also be a viscous liquid. In this patent application, “a fluid” is also understood to mean a cream, paste, gel, powdery substance and possible combinations thereof. Known examples are aerosol cans for dispensing an atomized liquid, vessels for dispensing liquids such as beer, bag-in-box for dispensing products suitable for consumption, such as coffee concentrate, ketchup, etc.
Thus, the prior art also includes packages filled with liquids and/or gases and/or powder, while the inner space of the package containing the product to be dispensed is pressurized for dispensing said products. For pressurizing the inner space, use can be made of, for instance, an inert propellant, such as nitrogen.
A device in the form of spray for an aerosol of the type described above is known from EP-A-0826608. In this known device, the pressure sensor element is provided with a chamber communicating with the outside air, which chamber accommodates a spring for generating said predetermined force. Included in the chamber is a diaphragm which is movable in axial direction of the chamber. On an inner side of the chamber, the spring presses against a first side of the diaphragm. On a second side of the diaphragm, opposite the first side of the diaphragm, a pin is attached to the diaphragm which, through up and down movement of the diaphragm, can close or release the fluid path. On the second side, the diaphragm is exposed to the pressure prevailing in the fluid flow path.
A problem of the known device is that it does not operate accurately during pressure control. In the known device, the diaphragm also influences the control of the gas pressure. Indeed, the diaphragm has a certain rigidity and a limited freedom of movement. Further, the spring provides rather an inaccurate reference force exerted on the diaphragm. This reference force codetermines the pressure set by the pressure control device. Further, the set pressure is also dependent on the atmospheric outside pressure to which the diaphragm is exposed.
EP-A-0 931 734 also discloses a pressure control device. This pressure control device is, however, not provided with a gas tight chamber. Instead it comprises a chamber which is in open communication with the outside world wherein a spring is provided in the chamber for obtaining an additional force.
EP-A-0 583 825 also discloses a pressure control device. This pressure control device, however, is accommodated in the diptube. Further, it applies that it comprises a plunger which is movable in a direction perpendicularly to the direction from the inflow opening to the outflow opening. This means that the closing and releasing of the fluid flow path take place in a particularly inaccurate manner. It also comprises a closing seal which is movable in a direction perpendicularly to the direction of the fluid path at the closing seal with the disadvantage.